﻿/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Lucene.Net.Codecs.Appending
{
    using System;
    using Index;
    using Store;

    /// <summary>
    /// Reads append-only terms from AppendingTermsWriter.
    /// 
    /// @lucene.experimental
    /// </summary>
    [Obsolete("Only for reading old Appending segments")]
    public class AppendingTermsReader : BlockTreeTermsReader
    {
        private const String APPENDING_TERMS_CODEC_NAME = "APPENDING_TERMS_DICT";
        private const String APPENDING_TERMS_INDEX_CODEC_NAME = "APPENDING_TERMS_INDEX";

        public AppendingTermsReader(Directory dir, FieldInfos fieldInfos, SegmentInfo info,
            PostingsReaderBase postingsReader,
            IOContext ioContext, String segmentSuffix, int indexDivisor)
            : base(dir, fieldInfos, info, postingsReader, ioContext, segmentSuffix, indexDivisor)
        {
        }

        protected override int ReadHeader(IndexInput input)
        {
            return CodecUtil.CheckHeader(input, APPENDING_TERMS_CODEC_NAME,
                BlockTreeTermsWriter.VERSION_START,
                BlockTreeTermsWriter.VERSION_CURRENT);
        }

        protected override int ReadIndexHeader(IndexInput input)
        {
            return CodecUtil.CheckHeader(input, APPENDING_TERMS_INDEX_CODEC_NAME,
                BlockTreeTermsWriter.VERSION_START,
                BlockTreeTermsWriter.VERSION_CURRENT);
        }

        protected override void SeekDir(IndexInput input, long dirOffset)
        {
            input.Seek(input.Length() - sizeof(long)/8);
            long offset = input.ReadLong();
            input.Seek(offset);
        }
    }
}
